The invention relates to an air-spring leg with a pressure chamber for motor vehicles, in which the pressure chamber can be subjected to different pressure via a connector leading to the outside.
In such an air-spring leg, a specific minimum pressure is to be maintained in the pressure chamber irrespective of any intentional or unintentional influences from the outside which may take effect in the chamber via a connection opening. Unintentional influences from the outside may occur, for example, due to system errors which may be triggered by defects in the valve or line or by faults in the electronic control system. In these cases, a certain emergency running capability of the vehicle is to be preserved by maintaining a minimum pressure. The desired minimum pressure is to be guaranteed on each spring leg of a vehicle.
A minimum pressure is also desirable in order, in cases in which the pressure chamber is formed by a spring bellows, to avoid damage to the air-spring bellows which could occur in an unpressurized state with specific, in particular single-layer, air-spring bellows with guidance at the outside.
The assurance of a minimum pressure is to be possible separately for each air-spring leg.
An object of the invention is to provide a functionally reliable and economically implementable solution to the objectives mentioned above. This object is achieved utilizing preferred embodiments of the invention wherein an automatically operating pressure relief valve is provided in the connector for maintaining a minimum pressure which can be predetermined for the pressure chamber, and wherein said pressure relief valve opens at a pressure which is acting from the interior of the pressure chamber or from the outside and is above the minimum pressure and closes at a pressure below the minimum pressure.
The pressure relief device provided according to the invention in the connector of each air-spring leg can basically be implemented in principle using pressure relief valves which are known per se. Embodiments, which can be produced in a particularly simple manner and act reliably, of a pressure relief valve which can be used for the purpose according to the invention are described in greater detail below with reference to an exemplary embodiment.
The provision according to the invention of the pressure chamber of each air-spring leg with a pressure relief valve directly in the pressure-chamber connector already allows the pressure chamber to be filled up to a predeterminable minimum pressure during the production of the compression-spring leg. The tightness of the pressure chamber can thereby be checked even before mounting of the spring legs on the vehicle. This is because, if there were any leakiness present, it would be possible to establish this by a lack of minimum pressure in the pressure chamber.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.